1. Field of the Invention
This invention relates to a method of enlarging an image field of a camera, such as a focal plane array camera. The image field, which consists of N pixels, is produced by combining scanned partial images which each consist of n pixels. The invention also relates to apparatuses for carrying out the method.
2. Discussion of Background Information
In order to record a large image field at high resolution using a camera, such as a focal plane array camera, it is necessary to use a detector, with a correspondingly large number of elements (pixels). This results in high costs, particularly with use of an IR detector. Alternatively, the large image field can be assembled from a plurality of smaller images which are displaced in relation to each other. This necessitates a “step-scan” mechanism, by which the optical axis is displaced from individual image to individual image but remains fixed during the recording time. This can be problematic, particularly with cameras which are mounted on a moveable platform for alignment. The step-by-step movement produces unwanted torque effects which can have an unfavorable effect on the alignment. Moreover, the step-by-step movement is associated with increased energy consumption.
A scanning principle has been employed in, for example, J. M. Lloyd, Thermal Imaging Systems, 1975, Plenum Press, N.Y. by using two rotating, refractive prisms. By suitably selecting the angle of deflection and the velocities of rotation, different scanning patterns can be created, which include, amongst others, an astroid pattern proposed according to the present invention. In the past, similar scanning patterns (cycloids) were employed for recording a 2-dimensional image field by an individual detector or a detector array.